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A pronounced difference in the behavior of heteroarm star copolymers from the conventional diblock copolymers is analyzed theoretically and experimentally on the example of symmetric polystyrene-poly(2-vinylpyridine) (PS6P2VP6) star block copolymer melts. Microphase separation of PS6P2VP6 stars with volume fraction of PS varying from 0.30 to 0.75 is studied using transmission electron microscopy (TEM). The observed (lamellar, cylindrical and undefined “bicontinuous-like”) structures often turned out to be different from that expected for the corresponding diblock copolymers. The dependence of the long period of lamellar structures of heteroarm star block copolymers on block length is found to deviate in a systematic way from N 2/3 law (known for diblock copolymers), especially for the stars of high functionality. The theoretical model proposed to describe an extra-stretching of star block copolymers near the lamellar interface is found to be successful in prediction of block length and star functionality dependence of the lamellar period as it agrees remarkably well with the present and other available experimental data for both symmetric and asymmetric heteroarm star block copolymers.

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tween the aligned MoO 6 octahedra, forming a sinusoidal pattern in a plane perpendicular to the oxide sheets; the phenyl rings, however, are tipped away from this plane about a dihedral angle of about ±13. This model was used in fitting the 1D data shown in Figure 2, and will also be used in our further studies to simulate the 2D Sync MAS data. Significantly, the polymer structure within the layers is similar to that of the oligoaniline ªpentamerº (five phenyl-ring molecule) determined by crystallographic studies. [14] The structure of PANI itself is not known, owing to its insolubility and lack of crystallinity.The 2 H NMR results provide substantial detail concerning the polymer in (PANI) 0.24 MoO 3 , as these show that order is not determined solely by the oxide layers, but is manifested by the polymer between the layers as well. The oxide host acts as a highly anisotropic 2D ªcageº that can be readily aligned on glass slides, which in turn can be oriented in the magnetic field. This allows the structure of the PANI chains to be probed as a function of orientation of the oxide host. Such a study is only possible in the nanocomposite, as bulk PANI cannot be oriented in a similar fashion. The combination of 1D and 2D Sync MAS 2 H NMR provides unique and irrefutable evidence as to the preferential orientation of polyaniline within the molybdenum trioxide host lattice. We add that the heterogeneity of the local carbon site environments along the polymer chain made characterization of order using high-resolution 13 C cross polarization (CP) MAS NMR fruitless. In contrast, solid-state 2 H NMR is uniquely suited to providing this information, by virtue of the large quadrupolar local field that dominates the spectra. Thus, 2 H NMR studies of polymers intercalated within transition metal oxide hosts can provide important and unique information about the structure of the polymer that cannot be obtained by other methods. Further investigations of these materials, including two-dimensional NMR experiments to better characterize the distribution [15] and electrochemical and NMR studies of lithium insertion in these materials, are ongoing. [5] Solid-state NMR spectra of perdeuterated polyaniline nanocomposites were performed at 11.7 T, for which the 2 H Larmor frequency was 76.77 MHz. The quadrupole echo pulse sequence was used, with 90 pulse widths of 2.0±2.2 ms when radio-frequency pulses of approximately 450 W were applied. As well, a much shorter pulse (0.5± 1.0 ms) was used for the initial excitation of the spins, with no difference due to finite pulse width effects evident in the spectra when compared to those obtained with the traditional 90±90 sequence. Acquisition was initiated before the peak of the quadrupole echo with subsequent left-shifting of the free-induction decay to ensure the peak of the echo was correctly obtained. Spectral widths of 1 MHz were used, corresponding to dwell times of 1 ms between each of the 8192 complex time-domain points collected.